kick the dog. In psychology , a description of displacement (a defense mechanism).

The classic case is a frustrated worker who is yelled at by his supervisor and cannot yell back. So he then comes home and “kicks the dog,” that is, he takes his frustrations out on someone else, probably a member of the family. The one most likely to receive this displaced anger might be the most vulnerable member of the family; or it may be the one perceived to be the most forgiving or trusted. Dogs, because of their non-human status and their fawning and obsequious nature, provide an easily understood proxy for the target of the anger.

The idea of taking out frustration on the dog in this manner is hardly a new one. On April 26, 1900 TheMassillon [Ohio] Independent printed a front page feature story about good coffee, actually advocating for a particular roaster who had advertised in another section of the paper. The unnamed writer notes that how the coffee lover reacts when the morning cup is “poor, 'sloppy,' bitter, black, muddly looking and only 'luke warm.'” The terms used to describe the coffee lovers' are quite in accord with contemporary psychological explanations: “You have a strong temptation to 'spank the baby,' kick the dog, quarrel with your mother-in-law... [etc.]”